1. Field of the Invention
This invention relates to radio frequency, millimeter-wave and microwave devices, and more specifically relates to a support structure, which maintains the relative spacing between conductors in such devices.
2. Description of the Prior Art
Radio frequency, millimeter-wave and microwave devices typically include one or more conductors internal to the device. The relative spacing and orientation of the conductors are often essential in maintaining a desired set of performance characteristics and design specifications for these devices. This is the case with microwave devices such as couplers, dividers, combiners and hybrids in which the relative distances between two or more conductors must be maintained to ensure that circuit characteristics are substantially constant over time, temperature, and handling.
Couplers can be used for such purposes as matching impedances or enabling two or more signals in different frequency bands to share a common transmission line. The latter type of coupler is commonly referred to in the art as a xe2x80x9ccross-band couplerxe2x80x9d. The cross-band coupler typically includes an enclosure, which houses separate conductors for the signals in the two bands, and a common conductor in which the signals from the two bands are alternately induced. Connectors mounted on an external surface of the enclosure provide a channel for the signals to pass from external cabling to the conductors inside the enclosure. The internal conductors are typically manufactured from copper rod.
Conventional methods of fixing the distance between conductors in a coupler involve the use of dielectric blocks. The dielectric blocks are milled or trimmed to a desired size, and a hole is drilled through the dielectric blocks which is about the size of the external circumference of the conductor. The dielectric blocks are then slid over the conductors, and the distance between adjacent conductors is adjusted or gapped to an appropriate value according to the coupling characteristics desired. Once the desired distance between the conductors is achieved, the blocks are affixed with adhesive to an internal surface of the enclosure.
The conventional method of spacing conductors just described presents many problems including losses and undesirable coupling though the dielectric blocks between the conductors, as well as between the conductors and the enclosure. In addition, gapping each coupler to achieve the desired spacing between the conductors is a difficult, costly, and time consuming task. Further, the dielectric, adhesive, or both typically move or change in dimension over time and temperature, which directly affects the performance characteristics of the coupler.
It is an object of the present invention to provide a radio frequency, millimeter-wave or microwave device and a method of making such a device, in which losses from and coupling between conductors internal to the device caused by a support structure for the conductors are negligible.
It is yet another object of the present invention to provide a support structure for conductors internal to radio frequency, millimeter-wave or microwave devices and a method of making such a device, which facilitates the manufacturing process of these devices, and enables these devices to maintain a substantially constant orientation of and spacing between the internal conductors regardless of aging, temperature, and handling.
It is yet a further object of the present invention to provide a coupler having at least a pair of spaced-apart conductors and a structure to support and maintain the spacing between them.
In accordance with one form of the present invention, a radio frequency, millimeter-wave or microwave device includes one or more internal conductors, and a support structure for the conductors. The support structure is preferably formed as a thin insulating sheet having oblong or oval-shaped holes cut through its thickness. The size of the holes and the spacing between adjacent holes in the sheet are selected to allow the conductors to be received by the holes and spaced apart a predetermined distance from each other.
The device includes a housing or enclosure in which the insulating sheet support structure and the conductors are situated. Preferably, the housing includes a base that is integral with four sidewalls and a removable cover, which define an interior cavity for housing the conductors and the support structure.
The insulating sheet support structure has a width such that the sheet extends partially above the top of the four sidewalls at an angle away from normal to the base when the conductors are disposed within the support structure. As the cover is mounted and secured on the four sidewalls of the device, it exerts a slight pressure on the edge of the insulating sheet, deflecting it slightly and holding the sheet in place within the cavity. The insulating sheet, in turn, secures the conductors in place within the housing and maintains the relative spacing between the conductors.
In accordance with another form of the present invention, a method of making a radio frequency, millimeter-wave or microwave device includes the steps of passing conductors through oblong holes in the support structure while the support structure is in an assembly position. The conductors are freely slidable within the holes while the support structure is in the assembly position. The support structure is then tilted away from the assembly position to a securing position, which is offset from normal to a longitudinal axis of the conductors. A force is then exerted on the support structure to maintain them in the securing position, which causes the external surfaces of the conductors to engage with the edges of the holes. Once in the securing position, the support structure maintains the relative spacing between the conductors within the enclosure.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in conjunction with the accompanying drawings.